1. Field of the Invention
This invention relates to a motor with a gear reducer, which is suitable for use as a wheel motor for vehicles, etc., and an assembly method and a maintenance method for the same.
2. Prior Art
Conventionally, there are known wheel motors for use as power sources of industrial vehicles including materials handling equipment, etc. These wheel motors for vehicles include an electric motor, a gear reducer for reducing a rotative driving force from the electric motor, and a housing accommodating the electric motor and the gear reducer.
Wheel motors of this kind, which are equipped with a gear reducer, especially require that the electric motor and the gear reducer should be mounted so as not to interfere with the body of a vehicle on which the wheel motor is mounted, when wheels of the vehicle move upward and downward or when the vehicle is turning. This raises a problem of a limited space within the vehicle in which the electric motor and the gear reducer are to be mounted. That is, the electric motor and the gear reducer have to be designed as compact in size as possible to enable them to be mounted in a limited space within the vehicle.
Further, to obtain a relatively high output from the motor for the weight of the vehicle body, the electric motor has to be designed to produce high output torque, though it should be designed compact in size and light in weight.
To meet these requirements, attempts have been made to arrange the rotor of the electric motor and the stator of the same such that the gap between them is reduced, and form the rotor of a high-performance permanent magnet material.
In assembling the conventional wheel motor with a gear reducer, however, when the rotor is put into a housing of the motor, the rotor can collide with the stator due to a large magnetic attraction force generated between the rotor and the stator, which can give damage to the surface of the permanent magnet forming the rotor or even break the same. To solve this problem, a wheel motor with a gear reducer has been proposed by Japanese Laid-Open Patent Publication (Kokai) No. 4-185532, which is easy to mount a rotor into a housing thereof. This proposed wheel motor is, however, still complicate in construction and requires rather complicated assembly steps.